What is a Firewall

What is a Firewall ?

Most commonly you would have came across a term call as a firewall while using internet.Let's see what does it really mean.

• A firewall can either be a hardware or a software.
• It can be called as a network security system that monitors and controls traffic to a private network based on some defined security rules.
• It blocks unwanted traffic and permits wanted traffics.

So what is traffic here?

• we commonly define traffic as the amount of data moving across a network at a given point of time.

In today's world every network(office,business) should have a firewall to keep their network safe.

• The one way that the firewall controls the flow of traffic in to and out of the network is by Access Control List(ACL).
• a ACL consist of the list of members who can access the network through the firewall.
• Example:

                    A firewall has the following ACL
                        165.43.99.03 --> Allow
                        172.15.16.10 -->Deny
                        45.90.172.66 --> Allow

• Then only the IP addresses 165.43.99.03 and 45.90.172.66 can access and pass through this firewall
• When ever 172.15.16.10 tries to access the firewall it blocks its request.

Some firewall comes with implicit deny rules.for example a firewall can allow only access to port 80 i.e. the websites.so we cannot access other things such as ftp , smtp etc..

• one of the example of the firewall is the Host based fire wall.
• It is a software based firewall.
• It is installed on a computer only and it protects that computer alone.
• Later versions of windows comes with host based firewall called as windows firewall.we can enable it or disable it as per our need.
• we can also install third party firewall softwares . such as Glash wire, zonealarm , peerblock etc..

• An another example of firewall is the network based firewall .
• It is a combination of hardware and software.
• It protects an entire network.

A real time application of firewall is that we know that some websites are not allowed in some countries .

• In this case all the ISP who are serving the internet to the users use a fire wall to block the users in that particular country from accessing the list of sites.

note: you can read my previous posts at  https://iamafutureprogrammer.blogspot.com/

If you have any queries ask in the comment section below.......Thank you ....